i am considering 5600+ on account of significantly lower power usage and great performance@price
also consider that this paired with a 8800gtx appears to handle all the latest games on high settings and high resolutions. one should be less concerned with cpu binding in upcoming games, especially when dx10 breaks through.
really the main examples of cpu binding for the 5000+ and upwards processors are for older games which you'd want to max out the resolution on anyways, games which you'll get 100+ fps in across several high resolutions.
granted the 2900xt is reported to beat the 8800gtx, i dont think it will be so radical as to be cpu bound in modern games by amd's higher end cpu's, and certainly not through the year